Doris Lessing, who died at home in London on Sunday at age 94, was a writer who refused to be categorized. Feminist, expatriate, experimentalist, realist, science-fiction writer: She was all of these and more.

Recipient of the 2007 Nobel Prize in literature, she is best known (rightly) for her 1962 novel "The Golden Notebook," the story of a fractured woman named Anna Wulf and her efforts to find some sort of integration. Lessing, however, later would see that book as something of an albatross, arguing that the artistry of the novel had been overlooked in favor of its politics.

Lessing was a political writer from the moment her first novel, "The Grass Is Singing," appeared in 1950. The book, published after she immigrated to England from colonial Rhodesia — where she'd been raised — involves a white farmer's wife who has an affair with a black servant; it was an audacious way to begin a career.

And yet, to consider it now, especially in comparison with "The Golden Notebook" or 1971's "Briefing for a Descent Into Hell," is to recognize just how traditional her early efforts were. As John Leonard suggested in the New York Review of Books: "After the passionate indignation and furious intelligence of the African stories, 'The Grass Is Singing' (1950), and the first four 'Children of Violence' novels, … Lessing stopped playing by the old narrative rules."

For Lessing, the act of writing was provoked in equal parts by rage and restlessness. She had no use for orthodoxy, of either the cultural or aesthetic kind. "The Golden Notebook" may have made her an early feminist icon, but she came to reject that label, lamenting in a 2008 interview that it "became the property of the feminists," when, in fact, her intentions were more broadly political. "I used to tire," she complained, "of having to explain to young readers in the 1970s what Khrushchev's speech to the 20th Congress meant to world communism. That's what really gave the book its charge."

Later, she would turn her back on Marxism, which she once characterized as "the sweetest dream," telling the Telegraph that "it was all a load of old socks. It seems incredible now that quite intelligent people believed in it all."

Of all the orthodoxies, perhaps those for which she had the least use involved literature. In wake of "The Golden Notebook," she moved in a more speculative direction, writing novels that adopted certain science-fiction tropes. "The Four-Gated City" (1969), which concludes her "Children of Violence" cycle, ends in 1997, in the midst of World War III. "The Memoirs of a Survivor" (1974) involves a retreat into an alternative universe.

Most notable of these speculative projects was "Canopus in Argos," a five-volume set of novels, published between 1979 and 1983, that comes framed as the galactic history of the Canopus empire, which seeks to influence the fates of other worlds (Earth included) while wrestling with issues of its own.

"It is by now commonplace to say that novelists everywhere are breaking the bonds of the realistic novel because what we all see around us becomes daily wilder, more fantastic, incredible," Lessing wrote in a preface to the first novel in the series, "Shikasta." Yet more to the point, she cited a much deeper tradition: that of sacred literature, and especially the Old Testament.

"Actually," she told the Paris Review in 1988, "it never crossed my mind with these later books that I was writing science fiction or anything of the kind! It was only when I was criticized for writing science fiction that I realized I was treading on sacred ground."

What she was saying, of course, is that literature should recognize no boundaries, that the best work moves us by challenging our preconceptions, whether they have to do with content or with form.

As she explains in her Paris Review interview: "I've met quite a lot of young people — some not so young either, if it comes to that — who say, 'I'm very sorry, but I've got no time for realism,' and I say, 'My God! But look at what you're missing! This is prejudice.' But they don't want to know about it. And I'm always meeting usually middle-aged people who say, 'I'm very sorry. I can't read your non-realistic writing.' I think it's a great pity."

This, in some ways, could be read as Lessing's legacy: Don't stand on ceremony, question your beliefs and prejudices and always, always be prepared to change your mind. In her later books, she returned to realism, but even as she became something of a revered figure, she reveled in her status as contrarian.

She was buying groceries when the announcement came that she had won the Nobel; when she returned home and was confronted by reporters, her response to the news was pointed: "Oh, Christ."

At age 88, she was the oldest winner of the prize, and the attention it brought her took its toll. "The whole thing is a joke," she grumbled in 2008, the year she published her last book, "Alfred and Emily."

"The Nobel Prize is run by a self-perpetuated committee. They vote for themselves and get the world's publishing industry to jump to their tune. I know several people who have won, and you don't do anything else for a year but Nobel. They are always coming out with new torments for me. Downstairs there are 500 things I have to sign for them."

The Nobel Prize in literature is awarded (almost) every fall to a writer for his or her body of work, and is considered the world's most prestigious literary award. The winner receives a medal and a cash prize of about $1.1 million.

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